A conventional PM type (Permanent Magnet Type) stepping motor 100 in which a permanent magnet is used in a rotor has been known as described, for example, in Japanese Patent Laid-Open No. 2004-112985.
A schematic structure of the conventional stepping motor will be described as follows with reference to FIG. 6. A pair of inner stator cores 104 for two phases are superposed on each other in a back-to-back manner. A plurality of pole teeth 106 is formed upright at an inner circumferential edge of the respective stator cores 104 at nearly equal intervals, and bobbin-less coils 110 are respectively mounted on the outer periphery of the pole teeth 106. A rotor 116 in which a magnet (permanent magnet) 114 is integrally fixed to a rotor shaft 112 is rotatably supported on mounting plates 120 through bearings 118 on an inner peripheral side of the pole teeth 106 of the inner stator cores 104.
Outer stator cores 122 are assembled to the inner stator cores 104 and a plurality of pole teeth is formed at an inner circumferential edge of the respective outer stator cores 122 so as to be alternately disposed to the pole teeth 106 of the inner stator core 104.
In the stepping motor 100 which is structured as described above, wire ends 110a of coils 110 are wound around terminal pins 102 provided on the respective inner stator cores 104. An electric current is supplied to the respective coils 110 through the terminal pins 102 and, as a result, a rotation drive force is applied to the rotor shaft 112 by generated magnetic field and rotation is outputted from one end side of the rotor shaft 112.
In the stepping motor 100 as described above, a terminal block 130 supporting the terminal pins 102 is mounted on the inner stator core 104 by adhesively bonding with an adhesive.
However, when the terminal block 130 is mounted by adhesively bonding with an adhesive, mounting position of the terminal block 130 on the inner stator core 104 may be easily displaced and the terminal block 130 may be easily mounted in an inclined state. In addition, the terminal block 130 is formed of resin and the inner stator core 104 is formed of metal and thus, when adhesive strength is low, a problem may occur, for example, the terminal block 130 is disengaged from the inner stator core 140.
As described above, when a problem such as displacement of the mounting position or disengagement of the terminal block 130 from the inner stator core 104 may occur due to low fixing strength of the terminal block 130 to the inner stator core 104, the wire end of the coil 110 connected to the terminal pin which is supported to the terminal block 130 may be disengaged or the wire end may be disconnected and thus an electric current is unable to be supplied to the coil 110 stably, which causes a problem in control for the stepping motor 100.